Bayer shares plunged more than 10 percent in morning trading Wednesday after a jury determined that a California man developed cancer from using the company’s Roundup weedkiller in his yard.

The case marked the second legal defeat in seven months for the German pharmaceutical giant over its weedkillers. Last summer, a separate jury hit the company with a $289 million judgment for failing to warn customers of the cancer risks tied to its Roundup and Ranger Pro brands. The penalty was later reduced to $78.5 million.

Bayer stock, which trades on the New York Stock Exchange, is down 34 percent since the first trial; that translates into $33.8 billion in lost market value.

“A third of the company has been wiped out since last July,” said Howard Silverblatt of S&P Dow Jones Indices. Bayer was worth $100.2 billion last July. In mid-day trading in the U.S. on Wednesday, the company was worth around $65 billion.

Bayer acquired Monsanto, the maker of the popular weedkiller, in June for $63 billion, merging Monsanto’s genetically modified crops with Bayer’s line of pesticides. The union created the largest seed and agrochemical company in the world.

Environmental advocates and customers have criticized Monsanto for years. And Bayer’s legal troubles are far from over: Several more trials are planned this year in California and Missouri, and the company potentially faces thousands of lawsuits from people whose farming and landscaping work brought them in direct, sustained exposure to Monsanto’s herbicides. The plaintiffs allege that Monsanto products are linked to their serious illnesses.

The latest trial in California will now enter its second phase. In the first stage, jurors determined that exposure to glyphosate — the active ingredient in Roundup — was a substantial factor in Edwin Hardeman’s cancer diagnosis. The California resident said he used the herbicide on his property for decades.

Jurors will now determine liability and damages. As Bloomberg reported, they will hear evidence that Monsanto manipulated public opinion to hide health concerns and boost sales.

Hardeman’s attorney did not immediately respond to a request for comment.

Bayer insists that Roundup products and their active ingredient are safe to use.

“We are disappointed with the jury’s initial decision, but we continue to believe firmly that the science confirms glyphosate-based herbicides do not cause cancer,” Bayer said in a statement Tuesday. “We are confident the evidence in phase two will show that Monsanto’s conduct has been appropriate and the company should not be liable for Mr. Hardeman’s cancer.”

Bayer also appeared to downplay the forward-looking significance of the legal defeat. The company said that even though it did not prevail in the first phase of the trial, the adverse decision won’t impact future cases and trials because each one contains its own factual and legal specifics.

“We have great sympathy for Mr. Hardeman and his family, but an extensive body of science supports the conclusion that Roundup was not the cause of his cancer. Bayer stands behind these products and will vigorously defend them.”

Bayer previously announced that it would discard the Monsanto brand name as part of a broader strategy to win back the trust of consumers. Bayer’s chief executive Werner Baumann has also said the company would work to engage in dialogue with the public, and “listen to our critics.”